Stephen Lo Wai-chung said those arrested were accused of disorderly conduct and crimes related to rioting, likely adding to complaints that the government is using such charges to intimidate political opponents and deter further protests.

Riot police patrol outside the Legislative Council (Kin Cheung/AP)

Yet the mostly young throngs of well-organised protesters seemed little deterred by such threats, even as they took pains to remain anonymous by wearing masks, declining to give their full names to journalists and using cash rather than stored value cards to buy subway tickets.

The demonstrations follow the 30th anniversary of China’s bloody suppression of the student-led pro-democracy protests centred on Beijing’s Tiananmen Square on June 4 1989.

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Protesters browse their smartphones near the Legislative Council (Kin Cheung/AP)

Mr Xi’s administration is also dealing with the trade war with the United States that has thrown its export-driven economic model into question, potentially threatening its relationship with China’s urban middle class that has been predicated on accepting strict political controls in exchange for improving standards of living.

As one of the world’s most important financial centres, Hong Kong also stands to suffer from the continuing impasse, adding to frustrations among young people over stagnating salaries and skyrocketing housing prices.

Heavy rain on Thursday morning kept fresh street protests from following those on Wednesday that shut down government headquarters and the Legislative Council on the day it was to debate the extradition bill.

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Riot police (KIn Cheung/AP)

Police kept a heavy presence around the government compound on Thursday while protesters sought to maintain pressure by blocking doors on subway trains and driving slowly on main roads.

In their black garb, use of social media and amorphous organisation demonstrators reflected the tactics of left-wing activists in Europe and the United States referred to as the Black Bloc, who have come to prominence at anti-globalisation and anti-capitalist protests such as that surrounding the 2017 G20 meeting in Hamburg.

Hong Kong’s chief executive Carrie Lam declared Wednesday’s violence “rioting” that was “intolerable in any civilised society that respects the rule of law”.

That designation could substantially increase the legal penalties for those arrested for taking part.

“Intense confrontation is surely not the solution to ease disputes and resolve controversies,” Ms Lam said.

Beijing has condemned the protests but so far not indicated whether it was planning harsher measures.

In past instances of unrest, the authorities have waited months or years before rounding up protest leaders.